I just found Leader Ultra Magnus on Amazon as well, which has a release date of August 31st. At this rate, wave 4 won't be out until Sept/October... if these Amazon dates are from Hasbro America.
Which seems a little strange. Hasbro America rushed out the first wave so fast that the comics weren't even ready, but now look to be spacing out the other three waves to make the series last until the end of the year.